Plasma processing apparatus and method

ABSTRACT

Disclosed herein is a plasma processing apparatus and a plasma processing method capable of performing plasma processing by performing temperature control of a sample table in accordance with a process step to be performed on a sample. The plasma processing apparatus performs plasma processing on a sample in accordance with a process recipe with the sample being placed on a sample table in which each of a plurality of areas is temperature-controlled by a temperature control means, wherein the process recipe includes a plurality of temperature setting parameters for the sample table, and the plasma processing is performed on the sample in accordance with the process recipe which is prepared for each of a plurality of process steps.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a plasma processing apparatusand, more particularly, to a plasma processing apparatus capable ofperforming temperature control of a sample table for placing thereon asample such as a semiconductor wafer for plasma processing.

[0002] For example, Japanese Patent Laid-open No. 2002-76103 disclosesthat, for the purpose of improving an accuracy in etching asemiconductor wafer, an interior of a sample table for placing thereon asample is divided into two parts of an inner part and an outer part, andcoolants having different temperatures are supplied separately to theinner part and the outer part to perform the etching with a temperaturegradient being applied to the sample table, thereby processing a surfaceof the semiconductor wafer uniformly.

[0003] An example of process recipes which have heretofore been used inthe plasma processing apparatus is shown in FIG. 7. As is apparent fromFIG. 7, temperatures set by a temperature control unit are irrespectiveof the etching recipe, and the set temperature of the inner part of thetable is always 20° C. and the set temperature of the outer part of thetable is always 0° C. It is possible to achieve a uniformity in finaletching amounts of the semiconductor wafer surface by positivelyapplying the temperature gradient to the sample table as mentionedabove, not by setting the whole sample table to a uniform temperature.

[0004] A comparison between final etching amounts of (a) a case ofsetting the whole sample table to 20° C. and (b) final etching amountsof a case of setting the inner part to 20° C. and the outer part to 0°C. is shown in FIG. 8. A final etching distribution in the case of (a)is in the shape of an inversed U (a curve), while that in the case of(b) is uniform. This is because, when a plurality of temperaturesettings for the sample table are varied from one another, considerablechanges are expected to occur in a reaction on and adsorption tosidefaces of an etching pattern although only minor changes occur incompositions of injected radicals and ions, influence of a densitydistribution of plasma, and intensity of the injections. That is to say,a reaction rate is increased with the temperature rise of the sampletable and an adhesion coefficient of reaction products to the sidefacesis decreased. As a result, the sidefaces become thinner by thetemperature rise to thereby enable a reduction in the etching amount. Onthe other hand, on a periphery of the etching pattern, the final etchingamount is increased because re-adhesion of the reaction products islikely to occur due to the temperature decrease of the semiconductorwafer.

[0005] In order to achieve high-performance and low power consumption ofsemiconductor devices, a gate length of the semiconductor devices isbeing made shorter every year. Since the gate length is an importantdimension which determines a device characteristic, it is called a CD(critical dimension) value or an etching amount. An allowable deviationof the gate length in a gate etching process is on the order of aseveral nanometers, and a slightest deviation in the manufacture processcan cause defects in the products. Further, since a diameter of thesample is being made larger and larger, a difference between an etchingresult of a central part of the sample and an etching result of aperipheral part of the sample is likely to occur. Therefore, there is ademand for elaborate temperature control which is suitable for theprocess.

SUMMARY OF THE INVENTION

[0006] The present invention has been made in view of the aboveproblems, and an object of the invention is to provide a plasmaprocessing apparatus capable of performing temperature control of asample table depending on a process performed on a sample for plasmaprocessing.

[0007] The present invention employs the following means in order tosolve the above problems.

[0008] The object of the present invention is achieved by a plasmaprocessing apparatus for performing plasma processing on a sample inaccordance with a process recipe with the sample being placed on asample table in which each of a plurality of areas istemperature-controlled by a temperature control means, wherein theprocess recipe includes a plurality of temperature setting parametersfor the sample table, and the plasma processing is performed on thesample in accordance with the process recipe which is prepared for eachof a plurality of process steps.

[0009] Further, the above object is achieved by a plasma processingapparatus for performing plasma processing on a sample in accordancewith a process recipe with the sample being placed on a sample table inwhich each of a plurality of areas is temperature-controlled by atemperature control unit, wherein the process recipe includes aplurality of temperature setting parameters for the sample table, andthe plasma processing is performed on the sample in accordance with theprocess recipe in which at least one of set temperatures of thetemperature setting parameters is altered in response to a processingresult of a preceding process performed on the sample, the processingresult being obtained prior to the plasma processing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other objects and advantages of the invention will becomeapparent from the following description of embodiments with reference tothe accompanying drawings in which:

[0011]FIG. 1 is a diagram showing an example of an etching apparatus towhich the present invention is applied;

[0012]FIG. 2 is a diagram showing an example of process recipesaccording to the present invention;

[0013]FIG. 3 is a diagram showing an example of an etching system usingthe etching apparatus to which the present invention is applied;

[0014]FIG. 4 is a flowchart from a step of photolithography to a step ofaltering a set temperature of a temperature control unit;

[0015]FIG. 5 is a flowchart from a step of inputting measured maskdimensions to a step of calculating a temperature correction value;

[0016]FIG. 6 is a diagram showing an example of an etching apparatus, towhich the present invention is applied, including a wafer temperaturesensor;

[0017]FIG. 7 is a diagram showing an example of conventional processrecipes; and

[0018]FIG. 8 is a diagram showing a comparison between final etchingamounts of a case of controlling the whole sample table to have auniform temperature and final etching amounts of a case of applying atemperature gradient to the sample table.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A first embodiment of the present invention will hereinafter bedescribed with reference to accompanying drawings.

[0020]FIG. 1 is diagram showing an example of an etching apparatus towhich the present invention is applied.

[0021] A sample to be etched such as a wafer 2 is placed on a sampletable 10 in an etching reactor 1. Various etching gases are supplied tothe etching reactor 1 from cylinders 3 via valves 4. The etching reactor1 has an air-tight structure so as to create a vacuum atmosphere byevacuating the reactor 1 using a vacuum pump (not shown) via an exhaustport 5 extending to a peripheral bottom of the etching reactor 1. Aplasma generation source 6 is used for generating plasma 7 in theetching reactor 1. A high frequency power source 9 for applyinginjection energy to ions in the plasma 7 and a direct current powersource 11 used for electrostatically attracting the wafer 2 on anelectrode are connected with an electrode support shaft 8 for supportingthe electrode. Coolant circulation paths 12 and 13 used for controllinga temperature of the sample table 10 are provided at an outer peripheralpart of the sample table 10, and coolant circulation paths 14 and 15 forcontrolling a temperature of the sample table 10 are provided at aninner peripheral part of the sample table 10. One end of each of thecoolant circulation paths 12 and 13 is connected to a temperaturecontrol unit 16, and one end of each of the coolant circulation paths 14and 15 is connected to a temperature control unit 17.

[0022] Although two temperature control units are used for controllingthe temperatures in the present embodiment, a plurality of coolants maybe prepared by using one temperature control unit and a temperatureconverter which is provided at a position midway of a circulation path.

[0023]FIG. 2 is a diagram showing an example of process recipes in thefirst embodiment of the present invention.

[0024] In a typical plasma processing apparatus, a controllermicrocomputer for a plasma processing apparatus controls devices andcomponents required for the process in accordance with a process recipein which many processing parameters such as processing time, a pressurein the vacuum reactor, power to be supplied to the plasma generationunit, process gas flow rates, and high frequency power to be applied tothe sample table are preset.

[0025] Also, in the case where the plasma processing for one substrateis performed through a plurality of divided process steps in such amanner that processing on a resist layer is performed in STEP 1,processing on a SiN layer is performed in STEP 2, and processing on apolysilicon layer is performed in STEP 3, the devices and components arecontrolled for processing in accordance with parameter settings of aprocess recipe for the next process step every time the process stepsare switched from one to another.

[0026] The present invention enables an optimum temperature control ofthe sample table for each of the process steps in view of the processsteps and types of layers by allowing a plurality of temperature settingparameters for the sample table to be included in each of the processrecipes for the process steps and by associating the sample table withthe process recipes. Thus, it is possible to control the final etchingamount of the wafer surface.

[0027] In addition, it is unnecessary to stop the temperature control ofthe sample table during a halt of the processing on the sample, and itis possible to perform the temperature control continuously on the settemperatures which have been employed in the preceding process step.Also, it is possible to perform the temperature control in advance ofprocessing on a next sample by setting the temperatures to the settemperatures which will be employed in a first process step of theprocessing on the next sample.

[0028] A second embodiment of the present invention will hereinafter bedescribed with reference to the accompanying drawings.

[0029] In general, it is usual to use the same recipe in the bulkproduction which is operated with the same process. This is becausesatisfactory reproducibility is achieved if plasma characteristic and soforth are kept at a constant level. Further, an alteration in a recipe(hereinafter referred to as “plasma recipe”) which influences on theplasma characteristic can be a waste of data which have been accumulatedby now. To find out a new optimum process recipe we must have trial anderror for which a considerable time and cost will be spent. However,even if the etching process is performed by using the same plasmarecipe, it is difficult to attain a constant etching result in somecases due to various disturbances such as changes with time andvariation in production caused in the subsequent process step.Therefore, the following configuration is employed in the presentembodiment in view of the above problems.

[0030]FIG. 3 is a diagram showing an example of an etching system usingan etching apparatus to which the present invention is applied.

[0031] An inspection device 31 is a CD-SEM (also called “lengthmeasuring SEM”) for measuring an etching amount of a sample of apreceding process step or a film thickness measurement instrument formeasuring a layer thickness, the CD-SEM and the instrument being usedprior to performing an etching process. An inspection device 32 servesto measure a final etching amount (etching amount after the etchingprocess). In the present embodiment, both of the inspection devices 31and 32 are CD-SEMs.

[0032] A database 33 accumulates relational expressions in which a settemperature of the sample table to be altered is calculated if aninspection result obtained by the aforementioned inspection and a targetetching amount which is an initial design value are given. Also, everytime the etching process is performed, the database 33 accumulates dataother than those described above, such as an etching amount of each ofthe layers in a preceding process (before the etching process), a finaletching amount, a final shape (shape after the etching process), plasmaemission during the process, and an etching rate.

[0033] A flowchart from a step of photolithography to a step of changingthe set temperature by the use of the temperature control unit is shownin FIG. 4.

[0034] A sample which has been subjected to a photolithography process(Step 41) undergoes the processing on a plurality of zones of ZONE 1 andZONE 2 branched for pre-measurement (hereinafter referred to as “CDpre-measurement”) of mask dimensions using the CD-SEM 31 (Steps 42 and43). Temperature correction value of the respective zones to be alteredare calculated from the CD pre-measurement results and the data storedin the database 33 including the target etching amounts, the types ofthe layers to be processed, etc. (Steps 45 and 46). The set temperaturesare altered after comparing the calculated temperature correction valueswith the set temperatures defined in the plasma recipe (Step 47).

[0035] Although the sample table temperature is divided into the innerpart temperature and the outer part temperature in the presentembodiment, the present invention is not limited thereto, and it ispossible to perform the temperature control by dividing the sample tableinto a larger number of areas.

[0036] A flowchart from a step of inputting measured mask dimensions toa step of calculating temperature correction values is shown in FIG. 5.

[0037] First of all, the target final etching amounts are inputted intothe database 33 (Step 52). The mask dimensions of the respective zonesare measured to be inputted into the database 33 (Step 51). Then, themeasured mask dimensions of the respective zones are compared with thetarget final etching amounts. A rate correction value of each of thezones can be calculated by, for example, dividing each of differencesobtained by the comparison by the etching time of STEP 1 (Steps 53 and54). As is apparent from FIG. 5, since the mask dimension measurementvalue (a) is larger than the target final etching amount (b), theetching process must be performed to be larger than the normal etchingamount. Then, temperature correction values of the respective zones arecalculated from the calculated rate correction values and the relationalexpressions of the types of the layers to be processed and thetemperatures of the sample table stored in the database 33 (Step 55).

[0038] An alteration unit (not shown) or the like for altering the settemperatures based on the database 33 and the temperature correctionvalues may be provided either in the etching apparatus or in theinspection device. Alternatively, the alteration unit may be connectedwith a host computer or the like which is linked to a network of asemiconductor manufacture line.

[0039] In the present invention, even if a deviation from a targetetching amount occurs on a product during a process preceding to theetching process, such as a photolithography process, it is possible toperform etching including corrections for achieving initial designvalues in the etching process owing to the above-describedconfiguration. Further, if the result of the etching is inspected, theinspection result is compared with the target final etching amount tothereby judge whether or not the current set temperatures of the sampletable are proper, and then the temperatures are properly altered untilthe desired etching amount is achieved, it is also possible toassimilate machine differences among etching apparatuses.

[0040] Further, since the variations in semiconductor surfaces, such asU-shape distribution and inversed U-shape distribution, are suppressedin the present embodiment by properly altering the temperatures of thesample table without altering the plasma recipe which influences on theplasma characteristic, the present embodiment is free from serious sideeffects.

[0041] In addition, although the case where the plasma recipe is notaltered is described in the present embodiment, it is apparent that thepresent invention is applicable to apparatuses in which the plasmarecipe is altered during the processing.

[0042] A third embodiment of the present invention will hereinafter bedescribed with reference to the accompanying drawings.

[0043]FIG. 5 is a diagram showing an example of an etching apparatus, towhich the present invention is applied, including a wafer temperaturesensor 62.

[0044] Conventional temperature control units for the sample tableperform a temperature control with respect to set temperatures bymonitoring coolants or the like by using a temperature sensor which isprovided in the temperature control units. However, the temperatures ofthe coolants monitored by the temperature control unit can sometimesdiffer from actual temperatures of a backface of a wafer. Also, for acomparison between a first wafer and a twenty-fifth wafer after thestart of processing, for example, the twenty-fifth wafer tends to behigh in temperature due to radiation heat from the etching reactor.Furthermore, since heat input is greater on an outer peripheral part ofthe wafer, the temperature of the outer peripheral part tends to behigher than that of a central part of the wafer. Therefore, in thepresent embodiment, the temperatures of the backface of the wafer aredirectly measured by the use of the wafer temperature sensor 62 or anelectrode temperature sensor (not shown) to provide the measurementresults as monitor values of the temperature control unit, therebyimproving an effect of controlling an etching amount of the wafersurface in each of processes, each of process steps, and each of layers.

[0045] While the invention has been described in its preferredembodiments, it is to be understood that the words which have been usedare words of description rather than limitation and that changes withinthe purview of the appended claims may be made without departing fromthe true scope and spirit of the invention in its broader aspects.

What is claimed is:
 1. A plasma processing apparatus for performingplasma processing on a sample in accordance with a process recipe withthe sample being placed on a sample table in which each of a pluralityof areas is temperature-controlled by a temperature control means,wherein the process recipe includes a plurality of temperature settingparameters for the sample table, and the plasma processing is performedon the sample in accordance with the process recipe which is preparedfor each of a plurality of process steps.
 2. A plasma processingapparatus for performing plasma processing on a sample in accordancewith a process recipe with the sample being placed on a sample table inwhich each of a plurality of areas is temperature-controlled by atemperature control means, wherein the process recipe includes aplurality of temperature setting parameters for the sample table, andthe plasma processing is performed on the sample in accordance with theprocess recipe for which at least one of set temperatures of thetemperature setting parameters is altered in response to a processingresult of a preceding process performed on the sample, the processingresult being obtained prior to the plasma processing.
 3. The plasmaprocessing apparatus according to claim 1 or 2, wherein the plasmaprocessing apparatus has a sample temperature measurement means or asample table temperature measurement means.
 4. The plasma processingapparatus according to any one of claims 1 to 3, wherein the pluralityof areas are an inner part and an outer part of the sample table.
 5. Aplasma processing method for performing plasma processing on a sample inaccordance with a process recipe with the sample being placed on asample table in which each of a plurality of areas istemperature-controlled by a temperature control means, wherein theprocess recipe includes a plurality of temperature setting parametersfor the sample table, and the plasma processing is performed on thesample in accordance with the process recipe which is prepared for eachof a plurality of process steps.
 6. A plasma processing method forperforming plasma processing on a sample in accordance with a processrecipe with the sample being placed on a sample table in which each of aplurality of areas is temperature-controlled by a temperature controlmeans, wherein the process recipe includes a plurality of temperaturesetting parameters for the sample table, and the plasma processing isperformed on the sample in accordance with the process recipe for whichat least one of set temperatures of the temperature setting parametersis altered in response to a processing result of a preceding processperformed on the sample, the processing result being obtained prior tothe plasma processing.
 7. The plasma processing method according toclaim 5 or 6, wherein the temperature control of the sample table isperformed by using a sample temperature measurement means or a sampletable temperature measurement means.
 8. The plasma processing methodaccording to any one of claims 5 to 7, wherein the plurality of areasare an inner part and an outer part of the sample table.